package com.hc.core.util;

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;

/**
 * Provides a helper that locates the declarated generics type of a class.
 */
public class GenericsUtils {

	/**
	 * Locates the first generic declaration on a class.
	 *
	 * @param clazz The class to introspect
	 * @return the first generic declaration, or <code>null</code> if cannot be determined
	 */
	public static Class getGenericClass(Class clazz) {
		return getGenericClass(clazz, 0);
	}

	/**
	 * Locates  generic declaration by index on a class.
	 *
	 * @param clazz clazz The class to introspect
	 * @param index the Index of the generic ddeclaration,start from 0.
	 */
	public static Class getGenericClass(Class clazz, int index) {
		Type genType = clazz.getGenericSuperclass();

		if (genType instanceof ParameterizedType) {
			Type[] params = ((ParameterizedType) genType).getActualTypeArguments();

			if ((params != null) && (params.length >= (index - 1))) {
				return (Class) params[index];
			}
		}
		return null;
	}
}
